Antenna system



Patented July 17, 1934 ANTENNA SYSTEM Enoch B. FerreIL Eaton Town, N. J., assignor to Bell Telephone Laboratories,

Incorporated,

'New York, N. Y., a corporation of New York Application December 1, 1930, Serial No. 499,212 4 Claims. (01. 250-33) This invention pertains to electrical measuring systems and apparatus, particularly to such as are adapted to measure the intensity of radio waves.

5 In radiant energy systems, including those-employing buried as well as aerial type of radiating or absorbing means, it is often desirable to measure accurately thestrength of the radio waves as actually radiated or as availablefor absorption, that is, as existent at a certain. point in the radiant energy path whether comprising ether or the earth. Ordinary measuring means directly inserted in antenna systems do not, in general, ac-

complish this. Moreover, present day measuring meansdisassociated from the antenna and employed for determining the actual wave intensity do not, in general, possess the desired degree of perfection because, amongother reasons, the absorption characteristic of the measuring means employed is not conducive to obtaining the desired result.

' In addition to accurately measuring the ether or, earth intensity of the radio wave, it is often desirable and convenient in certain systems to accurately determine at a location distantly located from the antenna the intensity of the wave in the antenna vicinity. For example,.in systems employing several transmitting or receiving antenna distantly located from each other and operated from a single control station, elficiency and ease of operation require that the operator at the control station be able to determine the ether intensities of the various waves, quickly and accurately. One object of this invention is to accurately measure the intensity of radio waves.

, Another object of. this invention isto measure at a single control point distantly located from the antennas and with a high degreeof accuracy, 0 theintensity of:radio waves transmitted from, or received by,Ione or several antennae. ,One feature of the invention resides in the use of an open-ended absorbing antenna, preferably of the directive type, which efiiciently translates 3 the energy'in the ether waves to a form of energy adapted to actuate electrical measuring apparatus. 1

Another feature of the invention theprovisionof means for insuring, a minimum transmission lossbetween the absorbing antenna and the indicating apparatus.

Still another feature of the invention is a means for suppressing earth eifects in the absorbing system.

I =..-'In'accordance withione embodiment of the invention a receiving antenna having a length preferably equal to substantially a half wave length of a radio wave desired to be measured, and symmetricallydesigned, is positioned relatively close to a transmitting antenna in the line of wave propagation. A thermocouple is connected to a voltage nodal pointof the receiving antenna, the particular nodal point. being also, preferably, the electrical balance point of the. antenna. In the case of an open half wave length antennasymmetrically placed with respect to the, earth, the thermocouple is connected to the antennamidpoint. The thermocouple is associated with a recording or registering device such as a galvanometer which may be located at a considerable distance from the thermocouple and may even be grounded." The transmission line conductors con necting the thermocouple and galvanometer each include a radio frequency choke coil.

The association of a thermocouplewith the receiving antenna at a voltage nodal point insures a current maximum flowin the receiving antenna and hence maximum temperature difference in the thermocouple. In addition, the connection to the midpoint or electricalbalance point of the antenna insures a minimum flow of radio frequency currentthrough the thermocouple'and galvanometer to ground, and hence a minimum loss in the absorbed energy. The chokecoils as-' sist in this function bytheir tendency to block or suppress any residual radio frequency current resulting, for example, from a slight unbalance.

The invention will be better understoodfrom in .connection the following description taken with the, drawing in which:

Fig. 1 illustrates a horizontal measuring antenna and associated measuring equipment;

Fig. 2 illustrates a measuring system employing a half wave length antenna of different shape than that of Fig. 1, the measuring equipment being connected to the antenna midpoint; and Fig. 3 illustrates an arrangement for, measuring at a single control station, the waves radiated from several antennae;

Referring to Fig. 1 reference numeral l-indi cates an open-ended horizontal measuring antenna, a multiple of a half wavelength long. The antenna is positioned in space so as to absorb a maximum amount of energy from a given radiated wave, and it is preferably placed at a considerable distance above the earth so as to minimize the antenna-to-earth efiect. At point A located an odd :quarter multiple of awave. length from one extremity 2 of the antenna 1,a thermocouple 3 is inserted. The thermocouple 3 is connected to a galvanometer 4 by means of transmission line conductors 5, each of which includes one of the radio frequency choke coils 6. The midpoint of the galvanometer coil is grounded through conductor 7. The ground connection is not necessary, but it is desirable for the purpose of removing static-and other pick-upv currents. The .letters m: andnt in the dimensional expression, represent integers, n being an odd integer.

Assuming that antenna 1 is positioned so as to absorb a maximum amount of energy from-at.

given wave, a current standing wave represented by dashed line 8 and a corresponding voltage-wave represented by dashed line 9.. are produoeclon the antenna. It current anti-nodal point. Irn viewvon-this fact, a maximum heating effect is obtained in the thermocouple 3. The thermocouple 3 causes a definite relation to the standing wave produced on theantenna; tO'IfiOW throughgalvanometer i. l'wtaidiofrequency choke: coils -6 functionto. prevent energy trom'lficwingi; between- :the antenna 1 and'zground; through" galvanometer 4; and thus materially decreaseitheiantenna tc-earth capacity efiect'.

InEigi: 2 ;referenceznumeral' e'indicates a measuring antenna a halt: wave length long bent .in the shape of. a U'. Atthe" approximate cente point B of'antenna' 9, athermocouple hi0 is insorted. This. thermocouple: is connectedrto galvanometeri l1: bynre'ansaof conductors 12' each of which includestone-of the radio frequency choke coils' 15. 'The midpoint of thegalvanometer coil is: grounded through conductor 14 for the purpose of removing undesired". energies: absorbed bythe line, and-for b'alaneingrthe. antenna with respect to ground. i Condensers; 15.: and '16 represent: the capacities between;v the ground and the: antenna portions at the left and: right of: point B respectively.

-Asin Fig... I the antenna shown in 'Fig. 2 is positioned so as to. 'efllcientlyabsorb energy from a given :radio wave. "Ihe'pointi'B is a current anti nod'a'l' point. of the resultant standingwwave, and it also the balance pointer the system. In other words, :if the antenna current-.is:;in the direction of arrows? 17; the currentifiowingfrom the r-ight hand p'ortion ofantenna' 9 :throughthe capacity repre'sent'ed by' condenser 16' to the ground and thence through theimeasuring equipment comprisingugalvanometer ll. and? associated conductors-back to the antennais: balanced by the curmnt flowlngfromrthe' left-handportion of the antenna through: the 'measuring :equipment to ground andthen'ce :tlroughthecapacity represented by condenser l5'toatheantenna. Arrows'ld and 19 represent; respectively, the direction of flow through imaginarycondensers l5 and '16 respectiwely'. ArrowsflO-representthe balaneedcurrent in conductor 1.4.: .Radio ire'quency choke coils 13 suppress any" unb alan'ced' radio frequency current=tending to flow overzc'onductors 12.

The system shown in Fig; 2' possessesdistinct advantages over Lrn'e'asuring systems: heretofore employed. First of: all 'bysassociatingthe-measuring equipment-with. a" voltage' nodall-point, a. galvanom'eter reading commensurate with the. maximum current :fl-ow iin the'znreasuring antenna is obtained. In= the 'second' place; the antennaetoearth curre'n-ts are red-ucedrto aaniinimnm by connecting the thermocouple 'to the" b'alance or symmetricalpoint or the antenna" "and including radid-frequency choke cons in the leads :from the thermocouple to *the galvanometer. *Finall'y,

will be seen that, point Allis-a wrective' transmi temperature" difference in direct current having a as compared to the system of Figure 1, the U shaped antenna absorbs vertically polarized, as well as horizontally polarized, wave components. Moreover, it permits more economy to be effected in supporting structure than the horizontal antenna of Figure 1.

In Fig. 3 a system-for measuring at asingle control= -station,'. waves: radiatedi' fromdifierent antennae, is illustrated. For purposes of illustration a directive short wave antenna system such as is disclosed in the copending application of E. J. Sterbaserial No. 382,103, filed July 30, 1929 and assigned" to the applicants assignee, is shown. Reference numeralsZland 22 indicate, respectivelyptheexciteriandreflector panels of such a dittingnantenna system. The exciter. panel is connected to the transmitter 23 by rrreansbi the conductors of transmission line 24.

Arrowfiindicates the direction of propagation of waves emanating from this antenna system. Referenoenumeralsfifi and 261 denote, respectively; the exciteri. and reflectoriipanels .of: another transmitting; antenna system; the. exciter panels being connected to the transmitter 27 by means of "transmission. tline; 28;and arrow DJ indicating the: directionxot propagationffrom this system.

' Reference numeral- 29 denotes a -U shaped measuring; antenna suclnaS shownin Fig.1 2 positionediin theplane of: polarization ofthewaves from the: antenna system: associatediwithtrans.- mitter 23' and numeral 30denoteS azthermocouple connected to the; antenna at. theiib'alance point, which point is also a current 'antienodal: point. Their-neasuring antennais connected. to aragalvanorneter in the controlv station 311 by meansof transmission line: 32. :R'eferencernumeral 33 reps resentsradio frequency choke coils inserted in the transmission line between the: measuring antenna 29: and control :station 31.

Similarly reference numerals 34; and 35 designate a U shaped measuring antenna and: associatedthermocouple, respectively, similar to the measuring antenna. 29 and thermocouple -30=just described. The measuring antenna 34inisnpositioned soas to: absorb the maximum-energy radiatedfrom the-antenna system associated with the transmitter 27." The thermocouple-:35-isinsertedin'antenna 34s at acurrent anti-nodal point which is also the .balance: point ofitheantenna, anditis-connectedto control station 31 by means of transmissionlinelBfi, the conductors of-whi'ch -each include-a. radio frequency ch'okeeoilv 37. Referencernurnerals 38 and 39 represent conductors of transmission lines connectings the control station 31" with. other measuring, antennae (not shownonxthet drawing).

The operation of. thesystem :shown' in Fig. 3 is obvious .fromzthe description given in connection with Figs. 1- and 2. The fieldstren'gth of the waves-radiated. by difierent antennaeincluding those associated with transmitters. 23 :and 27 may be simultaneously noted? or -recordedrby an operator at the centralized control station 31. In each-case an accurate reading is obtained inasmuch as only-:- arminimurn antenna current leaks: to ground from the measuring antennae and a reading corresponding to the maximum amplitude of the measuring antenna current is obtained. "The transmissionwloss =between= .the

measuring antenna and the control circuit isrrelatively small and is duefalmostz-ientirelyto. the

in Fig. 3 and in Figures 1 and' 2 are suitable for measuring a plurality of incoming waves and that radiation from directive or non-directive antenna may also be successfully measured.

It should also be understood that the invention is not limited to the type of antenna or type of measuring equipment illustrated, for an antenna having a different design or configuration from those shown, and other measuring equipment may be successfully employed without exceeding the scope of the invention.

What is claimed is:

1. A method of measuring the maximum intensity of the energy radiated by a transmitting antenna utilizing an open-ended U-shaped receiving antenna having a length approximately equal to a half-wave length of the radiated wave, which comprises positioning said receiving antenna so as to absorb immediately after emission, substantially, energy from both the horizontally and vertically polarized components of the radiated Wave, and measuring the resulting standing wave on said receiving antenna at the current anti-nodal point.

2. A system for measuring the maximum intensity of a radio Wave emitted by a transmitting antenna comprising an open-ended U-shaped antenna positioned in the plane of polarization of said wave and closely adjacent to said transmitting antenna and a current indicator electrically associated with a current anti-nodal point of plane of Wave polarization and having a length substantially equal to an odd multiple of a half of said wave length, a thermocouple connected to the approximate midpoint of said open-ended antenna, a galvanometer, leads connecting the thermocouple and galvanometer, said leads including a radio frequency choke coil, and a lead connecting the galvanometer to ground.

4. A system for measuring the intensities of a plurality of waves comprisingin combination a plurality of antennae for propagating different radio wave trains, a plurality of open-ended antennae each positioned relatively close to one of the said antennae in the plane of polarization of the wave transmitted from the associated antenna, a separate current measuring means associated with the voltage nodal point of each of the antennae, radio frequency choke coils included between each measuring means and its associated open-ended antenna, said measuring means being located at one control point.

ENOCH B. FERRELL'. 

